Get out your green on Monday: It's St. Patrick's Day. USA TODAY Network explains the origins of some of the Irish holiday's traditions.

Who was St. Patrick?

St. Patrick — brace yourself — was not actually Irish.

Patrick was a nobleman born in about 400 A.D. in Britain and kidnapped by Irish pirates at the age of 16, said Philip Freeman, author of St. Patrick of Ireland: A Biography.

A stained glass window of St. Patrick at the St. Thomas Aquinas Church in Brooklyn, N.Y.(Photo: St. Thomas Aquinas Church)

Patrick was born into a religious family, but was an atheist early in his life. However, he rediscovered his faith while enslaved in Ireland, Freeman told USA TODAY Network.

After 17 years as a slave, St. Patrick escaped Ireland and found his way home, but returned to Ireland as a missionary.

"He said he was ready to die in Ireland in order to make his mission successful," Freeman said.

It's unclear if St. Patrick did in fact die in Ireland, but March 17 is widely believed to be the day of his death, according to Freeman.

Bagpipers play in the annual St. Patrick's Day parade along Fifth Avenue in Manhattan on March 17. Political controversy surrounded this year's parade, as New York City Mayor Bill de Blasio decided not to march due to the parade organizers' policy to ban participants that identify themselves as lesbian, gay, bisexual or transgender. Andrew Burton, Getty Images

Brenda Meyers kisses a member of the Yonkers Firefighters Pipes and Drums during Savannah, Ga.'s 190-year-old St. Patrick's Day parade. Kissing men in uniform is a tradition during the celebration. Stephen B. Morton, AP

Kelley Nolan and her husband Ken Myers dress the part during the St. Patrick's Day parade in Savannah, Ga. Despite a constant drizzle of rain, the couple still cheered as the parade passed through historic downtown. Stephen B. Morton, AP

A cadet from the Benedictine Military School gets kissed by a young woman during the St. Patrick's Day parade in Savannah, Ga. Kissing men in uniform is a tradition during the celebration in Georgia's first city. Stephen B. Morton, AP

Members of the New York Police Department march past protesters during the St. Patrick's Day parade. The banner reads, "Boycott Homophobia." Parade organizers said gay and lesbian groups were not prohibited from marching, but they could not carry gay-friendly signs or identify themselves as being gay. Mark Lennihan, AP

This woman takes part in the St. Patrick's Day Parade in Berlin on March 16. St. Patrick is considered the patron saint of Ireland, but parades in his honor take place around the world. Wolfgang Kumm, epa

Irish setters and their owners are ready at the start of the 22nd St. Patrick's Day Parade at Omotesando fashion district in Tokyo. Some 1,000 people took part in the annual parade. Toru Yamanaka, AFP/Getty Images

Staying out of hot weather, Mike and Edina Tarango drink beer at the annual Porterville Breakfast Lions Club St. Patrick's Day Brewfest at Veteran's Memorial Building in Porterville, Calif., on March 15. Chieko Hara, AP

Romanian traditional bagpipe musicians perform old traditional songs with instruments made from goats, as the parade's special guests, during a St. Patrick's Day street parade held in downtown Bucharest. Mihai Barbu, epa

Drag queen Peachy Queen poses from the back of a bus, and prepares to march in the St. Patrick's Day parade on behalf of all gay, lesbian, bisexual and transgender people on March 16 in Sydney. Don Arnold, Getty Images

The first recorded mention of a leprechaun goes back to the 8th century, coming from the word luchorpán, meaning "little body" to describe water spirits, according to John and Caitlin Matthews in The Element Encyclopedia of Magical Creatures.

Another possible origin is the Irish god Lugh, whose Welch variant is known as one of the "Three Golden Shoemakers."

There's also the Irish fairy Cluricaune, "a cunning spirit who haunts cellars, drinks, smokes and plays tricks," the Matthewses write. Cluricaune was popularized in a 1825 publication called Fairy Legends.

Corned beef and cabbage

Although a classic St. Patrick's Day meal, corned beef and cabbage is more American than Irish.

Irish Americans in the 19th century were mostly poor. The most affordable meat available was corned beef, according to Cronin.

And cabbage? "It's a spring vegetable and it's cheap," Cronin said.

Guinness

The Irish stout is the drink of choice on St. Patrick's Day.

A pint of Guinness beer.(Photo: Leon Neal, AFP/Getty Images)

On a typical day, Americans drink about 600,000 pints of the Dublin-based beer. But on St. Patrick's Day, about 3 million pints of Guinness are downed, according to Guinness in an email to USA TODAY Network.

Planning on drinking a pint on Monday? Tips from Guinness on the perfect pour: Tilt the glass at 45 degrees when pouring until it is three-quarters full, then let the beer settle before filling the glass completely to the top.